JPH07153464A - Nickel electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide a nickel electrode plate for an alkaline storage battery suppressing the swelling caused by an electric charge and an electric discharge and having a high energy density and a long life by using a specific nickel hydroxide powder as an active material. CONSTITUTION:The nickel hydroxide powder having the true density of 3.8-4.0g/cc is used as an active material. A nickel nitrate aqueous solution and a sodium hydroxide aqueous solution are dripped into an aqueous solution kept in weak alkali, stirred, washed with water, and dried to obtain the nickel hydroxide powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nickel electrode plate for an alkaline storage battery.

[0002]

2. Description of the Related Art Conventionally, in an alkaline storage battery for a nickel / cadmium storage battery or a nickel / hydrogen storage battery, the positive electrode has a sintering type in which an active material is filled in a porous substrate obtained by sintering nickel powder into punching metal or the like. Nickel plates have been used. When the porous substrate used for the sintered electrode plate has a high porosity, its strength becomes weak, so that it is difficult to set the porosity to 90% or more. Therefore, there is a limit to increasing the porosity of the substrate and increasing the filling amount of the active material in order to increase the energy density of the electrode plate.
Further, the sintered electrode plate has a problem that the process of filling the active material is complicated.

Therefore, in order to solve the above problems, a non-sintering type manufacturing method is used in which the active material powder is directly filled in sponge nickel or the like. The non-sintered electrode plate is a plate that can achieve high energy density and that can be easily filled with an active material. However, even in such a non-sintered manufacturing method, further higher energy density and longer life of the electrode plate are required. In order to achieve such a requirement, the nickel hydroxide powder used for the electrode plate is required to have the following characteristics. Nickel hydroxide powder has high electrochemical properties to obtain high electrode plate utilization. The apparent density of the nickel hydroxide powder is high in order to obtain a high active material packing density of the electrode plate. In order to prevent expansion of the electrode plate caused by repeated charging and discharging, the volume change of the nickel hydroxide powder during charging and discharging should be small.

In order to obtain a nickel hydroxide powder satisfying such requirements, there is a method of defining the specific surface area and the pore volume (pore volume) of the nickel hydroxide powder. This is because the larger the specific surface area of nickel hydroxide, the higher the electrochemical characteristics, the smaller the specific surface area, the smaller the increase in volume due to charge / discharge, and the smaller the pore volume, the larger the apparent density. .

In the electrode plates disclosed in JP-A-1-187768 and JP-A-5-41212, the physical properties such as specific surface area and pore volume are defined to improve the characteristics of the active material. I am trying.

[0006]

However, the conventional method has the following problems. As described above, when the specific surface area of nickel hydroxide is increased, the electrochemical characteristics are improved, but the volume increase due to charging / discharging is increased. The chemical properties are reduced.

Also, the relationship between the pore volume and the specific surface area is
If one increases, the other also increases, and if one decreases,
The other is also in a decreasing relationship. Therefore, if the pore volume is reduced in order to increase the apparent density and the packing density of the active material, the specific surface area also decreases, and the electrochemical characteristics cannot be improved as desired. Conversely, if the specific surface area is increased to improve the electrochemical characteristics, the packing density of the active material cannot be increased.

As described above, the conventional methods for defining the specific surface area and the pore volume have a problem that it is difficult to adjust the physical properties to satisfy the requirements for higher energy and longer life of the electrode plate. It was The present invention has been made in view of the above problems, and provides a polar plate having high energy density and long life, which defines new physical properties in addition to the physical properties conventionally defined for nickel hydroxide powder. With the goal.

[0009]

To achieve the above object, in the present invention, a nickel hydroxide powder having a true density of 3.8 to 4.0 g / cc as an active material of a nickel electrode plate for an alkaline storage battery. Is used.

[0010]

The nickel hydroxide powder is composed of a solid part and voids, and the smaller the total volume of the voids, the higher the apparent density. By using this powder, an electrode plate having a high packing density of the active material can be obtained. It will be possible to obtain. Further, the solid part characteristics can be classified into surface characteristics (mainly surface area) and internal characteristics.

Of these, the surface characteristics are closely related to the volume of the hole portion as described above, and are determined by defining the volume of the hole portion. In the electrode plate of the present invention, the true density is newly defined as the physical property of the solid portion of the active material. The true density of a powder is important information for knowing the characteristics of the solid part of the powder, and is a physical property indicating the degree of intrusion of crystals and disordered substances such as water.

The true density does not depend on the characteristics of the pores even if the characteristics of the same solid portion are the same as the characteristics of the surface. By defining the true density to be 3.8 to 4.0 g / cc, a nickel hydroxide powder having high electric characteristics and having a small volume increase due to charge and discharge can be obtained. By using this nickel powder as an active material, It is possible to obtain an electrode plate having high energy density and long life.

Furthermore, since the pore volume can be defined regardless of the true density, the true density is defined as described above, and the pore volume can be reduced to further increase the energy density of the electrode plate. it can.

[0014]

【Example】

(Example) An example according to an example of the present invention will be described below. The electrode plate of this example was manufactured as follows. First, nickel hydroxide powder (true density of 3.9 g
/ Cc, pore volume (pore volume) 0.03 cc / g, pore diameter (pore diameter) 41 Å) 85% by weight, and 1% by weight methylcellulose aqueous solution is activated on an active material consisting of 15% by weight of cobalt hydroxide powder. An active material slurry was prepared by mixing 60% by weight with the material powder. Next, the active material slurry was filled in a sponge-like nickel substrate and dried and rolled to prepare an electrode plate.

The nickel hydroxide used as the above active material was prepared as follows. [Preparation of Nickel Hydroxide Powder] An aqueous solution of nickel nitrate and an aqueous solution of sodium hydroxide are dropped into an aqueous solution kept weakly alkaline, stirred, washed with water, and dried to obtain the above true density of 3.9 g / cc. Pore volume 0.03c
A nickel powder having a c / g and a pore diameter of 41Å was prepared.

The true density of the powder was measured by introducing a known weight of the powder into a constant volume of helium gas and measuring the volume change of the helium gas (so-called helium gas replacement method). (Experiment) In order to know the relationship between the true density and the characteristics of the electrode plate, the electrode plate of the above-mentioned example and an electrode plate using nickel hydroxide having various different true densities as an active material were prepared. The electrode plate utilization rate and the electrode plate swelling rate of the plate were investigated, and the results are shown in Table 2. In addition, in order to change the true density of nickel hydroxide, p of alkaline solution at the time of nickel hydroxide preparation
H, the reaction temperature, and the stirring intensity were variously changed. The electrode plate was manufactured in the same manner as in the above example.

Further, a cell for measuring electrode plate characteristics was prepared as follows. Each electrode plate was combined with a known sintered cadmium electrode plate through a nylon non-woven separator, and this was immersed in an aqueous potassium hydroxide solution to prepare a cell for measuring electrode plate characteristics. Table 1 below shows the thus prepared
The physical properties of nickel hydroxide used in the electrode plate of the electrode plate characteristic measuring cell are shown below. The cell name is attached and the descending order of the true density _{(A 1) ~ (A 6} ).

[0018]

[Table 1]

The experimental conditions are as follows. (Measurement of electrode plate utilization rate) The above electrode plate characteristic measuring cell was charged and discharged under the following conditions to calculate the electrode plate utilization rate. Charge: 0.1 C (vs electrode plate theoretical capacity) × 16H Discharge: 0.25 C (vs electrode plate theoretical capacity) discharge to 0.8 V (measurement of electrode plate swelling ratio) After charging and discharging under the conditions, the expansion rate of the electrode plate was measured by measuring the thickness of the nickel electrode plate.

Charge: 0.1 C (vs electrode plate theoretical capacity) × 1
Week discharge: Discharge up to 0.8V at 0.25C (vs electrode plate theoretical capacity)

[0021]

[Table 2]

As is clear from Table 2, regarding the utilization rate of the electrode plates, utilization efficiency of 90% or more was obtained except for the electrode plates used in the (A ₁ ) cell. From this result, the true density is 4.0 g /
It can be seen that good electrode plate utilization can be obtained at cc or less. Regarding the swelling rate of the electrode plate, (A ₅ ) and (A ₆ )
The swelling rate of the electrode plate of the cell is high, and the true density is 3.
It can be seen that 8 g / cc or more is effective.

From the above results, it is desirable that the true density of the nickel hydroxide powder used is 3.8 to 4.0 g / cc in order to produce an electrode plate having a high utilization rate and a small expansion. I understood. Further, the filling capacity is considered to be sufficiently high because the pore volumes are all small.

[0024]

As described above, according to the present invention, by using nickel hydroxide having a true density of 3.8 to 4.0 g / cc as an active material, a high energy density and a long life can be obtained. The effect that a board can be produced is produced.

Claims (1)

[Claims] 1. A nickel electrode plate for an alkaline storage battery, wherein nickel hydroxide powder having a true density of 3.8 to 4.0 g / cc is used as an active material.